The present invention relates to a multi-optical-path photoelectric switch having a light emitting portion incorporating a plurality of light emitting devices and a light receiving portion having the same number of light receiving devices as that of the light emitting devices.
As a photoelectric switch for detecting a predetermined area, a multi-optical-path photoelectric switch is known which is structured as shown in FIG. 10 and which incorporates optical paths, the number of which can be varied. FIG. 10 is a perspective view showing a multi-optical-path photoelectric switch having six optical paths or channels, the multi-optical-path photoelectric switch having a light emitting portion 51 and a light receiving portion 52 disposed opposite to each other. The light emitting portion 51 has six light emitting devices (not shown). The light receiving portion 52 has six light receiving devices 53a to 53f therein. The light emitting devices and the corresponding light receiving devices 53a to 53f are structured such that their optical paths coincide with each other. The light receiving portion 52 incorporates a main unit 54, an extension unit 55 which can be connected to the main unit 54 and mutually, and an end unit 56 which can be connected to the extension unit 55 and the main unit 54.
FIG. 11 is a diagram showing the assembled light receiving portion 52 of the multi-optical-path photoelectric switch shown in FIG. 10. The main unit 54 has a stepped portion in substantially the central portion thereof and incorporates a large-diameter portion 54a and a small-diameter portion 54b formed integrally with the large-diameter portion 54a. The small-diameter portion 54b has an engaging projection 54c and a guide groove 54d. The extension unit 55 has a stepped portion in substantially the central portion thereof and incorporates a hollow joint portion 55a and a light-receiving-portion joining portion 55c formed integrally with the joint portion 55a. An engaging hole 55b to which an engaging projection 54c of the main unit 54 is engaged is formed in the side surface of the hollow joint portion 55a. The light-receiving-portion joining portion 55c has an engaging projection 55d and a guide groove 55d. An engaging hole 56a to which the engaging projection 55d of the extension unit 55 is engaged is formed in the side surface of the end unit 56.
When the foregoing units are assembled into the multi-optical-path photoelectric switch, the small-diameter portion 54b of the main unit 54 is inserted into the joint portion 55a of the extension unit 55. Then, a projection (not shown) of the extension unit 55 is slid in the guide groove 54d so that the main unit 54 and the extension unit 55 are connected to each other. At this time, a female connector provided for either of the foregoing units and a male connector provided for the other unit are connected to each other. Moreover, the light-receiving-portion joining portion 55c of the extension unit 55 is inserted into the end unit 56 so as to slide a projection (not shown) of the end unit 56 in the guide groove 55e. Thus, the extension unit 55 and the end unit 56 are connected to each other. At this time, a female connector provided for either of the foregoing units and a male connector provided for the other unit are connected to each other. As a result, the main unit 54, the extension unit 55 and the end unit 56 are mechanically and electrically connected to one another.
Each of the main unit 54, the extension unit 55 and the end unit 56 of the multi-optical-path photoelectric switch shown in FIG. 10 is made of a member obtained by molding, for example, synthetic resin. Therefore, there arises problems in that realized rigidity is insufficient to obtain satisfactory mechanical durability against external oscillations and impact. If the number of units which must be connected to one another increases and thus the overall length of the multi-optical-path photoelectric switch is elongated, there arises a problem in that the strength of the intermediate portion of the multi-optical-path photoelectric switch for maintaining the connection among units becomes unsatisfactory.